Re: [PATCH] powerpc/mm: tell if a bad page fault on data is read or write.
From: Michael Ellerman <mpe@ellerman.id.au>
Date: 2019-08-29 12:14:45
Also in:
lkml
Christophe Leroy [off-list ref] writes:
DSISR has a bit to tell if the fault is due to a read or a write.
Except some CPUs don't have a DSISR? Which is why we have page_fault_is_write() that's used in __do_page_fault(). Or is that old cruft? I see eg. in head_40x.S we pass r5=0 for error code, and we don't set regs->dsisr anywhere AFAICS. So it might just contain some junk. cheers
quoted hunk ↗ jump to hunk
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c index 8432c281de92..b5047f9b5dec 100644 --- a/arch/powerpc/mm/fault.c +++ b/arch/powerpc/mm/fault.c@@ -645,6 +645,7 @@ NOKPROBE_SYMBOL(do_page_fault); void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) { const struct exception_table_entry *entry; + int is_write = page_fault_is_write(regs->dsisr); /* Are we prepared to handle this fault? */ if ((entry = search_exception_tables(regs->nip)) != NULL) {@@ -658,9 +659,10 @@ void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) case 0x300: case 0x380: case 0xe00: - pr_alert("BUG: %s at 0x%08lx\n", + pr_alert("BUG: %s on %s at 0x%08lx\n", regs->dar < PAGE_SIZE ? "Kernel NULL pointer dereference" : - "Unable to handle kernel data access", regs->dar); + "Unable to handle kernel data access", + is_write ? "write" : "read", regs->dar);
break; case 0x400: case 0x480: -- 2.13.3